Final answer:
The mitochondria are specialized structures within a cell responsible for producing ATP, the main energy-carrying molecule, through the process of cellular respiration.
Step-by-step explanation:
The part of the cell that is a specialized structure to produce energy is the mitochondria. Mitochondria, often referred to as the "powerhouses" or "energy factories" of a cell, are responsible for making adenosine triphosphate (ATP), which is the main energy-carrying molecule of the cell.
Within the mitochondria, energy-carrying molecules from food are transformed through biochemical reactions into the usable form of cellular energy, ATP, in a process known as cellular respiration. Cells with high energy needs, such as active muscle cells, have many mitochondria, while cells with lower energy needs have fewer mitochondria. The presence of two lipid bilayer membranes along with various molecules along the inner membrane support the mitochondrion's function of energy production.